Harness energy from compressed air and turn heat into profit

Nearly all of the energy used to power air compressors gets converted to heat and this heat source can be harnessed to financial benefit of your business, says Mark Whitmore

Author: Mark Whitmore, general manager, BOGE Compressors Ltd

Cutting energy consumption is almost always the best way to enhance plant efficiency and there are now a number of tools available with which to evaluate, manage and reduce consumption. For example, nearly all of the energy that is used to power an air compressor gets converted to heat and you can harness this heat source to the financial benefit of your business.

To evaluate efficiency, good diagnostic information is essential. This will ensure that problems are detected early enough to allow planned maintenance intervention or repair to be carried out with minimal disruption, reducing overall maintenance costs, improving safety and increasing both plant availability and product quality.

Today’s designers and engineers have developed a wide range of portable and online tools to monitor various parameters. With the help of these tools you can swiftly determine how your critical equipment is running and identify early any operational problems so that they can be addressed at a time convenient to you or the production process, thus maximising asset performance and efficiency.

With a growing number of systems now incorporating their own diagnostic tools, companies should review the options to take advantage of the best possible opportunities. In particular, the increased use of electronics in compressors means that energy efficiency can be enhanced. This is because switching behaviour is optimised through the use of using intelligent control systems. Rising electricity prices over recent years have added yet another challenge to those striving to maintain profitability and running a lean business has rarely been so difficult, but compressor diagnostics are developing fast to help manage the cost of energy.

The combination of status checks and remote monitoring enables the provider to offer service and contractual arrangements that are better tailored – and more cost-effective – for the customer’s needs. For example, customers can now invest in a ‘total responsibility’ service contract, in addition to warranties on all the components of the compressor that can last as long as five years. And such are the enhanced capabilities of compressor diagnostics that they are set to raise the duration of warranties to the ten-year mark.

The move is towards service contracts that are better value for the user, based on a more modular concept. If customers can select the modules that are most important to them, such as remote maintenance and fault diagnostics, and add these to their service contract as additional modules without immediately having to sign a full service contract, then solutions can be tailored to the customer’s specific requirements and budget.

Machine failure, typically the result of incorrect installation and maintenance of components and equipment rather than normal wear and tear, can be easily prevented by applying advanced, but not necessarily expensive, diagnostic tools. Such tools enable efficient predictive maintenance, and the long term reliability of countless manufacturing and process systems depend on it. Monitoring devices enable plant operators to react swiftly to impending failures within the system and therefore an effective monitoring regime is an essential part of any machine maintenance programme.

Compressed air and heat recovery

Mark Whitmore

However, it is the cost of energy that causes the greatest threat to profitability. With businesses being squeezed between rising commodity prices and blistering competition, the era of largely ignoring resource costs is over. However, one option that provides a powerful, energy-saving opportunity for many compressed air users is waste-heat recovery.

According to figures from the Carbon Trust, over 90% of the electrical energy used by a typical air compressor is lost as heat. Being able to capture and reuse this energy for space heating, water heating or for other production duties therefore offers real benefits for businesses and is in step with the view being taken across industry that a broader, more holistic view must be taken when it comes to energy efficiency.

The technology of heat recovery is developing fast to help recoup the cost of energy and is now being applied on a large scale. For example, an innovative heat recovery scheme in the UK will provide warmth for local homes by channelling waste heat from London Underground tunnels. The London Underground system generates large amounts of heat and that is to be captured from a Northern Line vent and piped into the heat network. It is hoped that the project will reduce bills and lower carbon emissions, as well as drive innovation, jobs and growth in what looks to be a burgeoning sector.

For businesses, there are a number of avenues to explore when it comes to heat recovery. One option that provides an energy-saving opportunity for many compressed air users is waste-heat recovery.

Waste heat recovery for compressors

Energy from compressed air

Because almost the entire energy consumption from the supply net of a standard compressor is converted into heat there is a correspondingly high degree of energy available for heat recovery. Take, for example, an oil-lubricated screw compressor: up to 94% of the electrical energy input to this equipment is available for heat recovery.

This waste heat generated by the compressor can be re-directed into heating spaces, just as it is in the London Underground initiative. This is especially efficient in plants where the compressor is within the vicinity of the area being heated – for example, in a workshop where the compressor is stationed, or by the use of ducting where the compressor is in a more remote location.

It is also possible to extract waste heat from the compressor to heat water for use in central heating or boiler systems, industrial cleaning processes, plating, operations, heat pumps, laundries, or any other application where hot water is required.

For businesses that are considering investment in heat recovery, a compressor specialist can help calculate the potential energy and cost savings to highlight the possible payback in terms of the immediate reductions in fuel, oil and gas costs. The benefits are typically striking – for example, some heat-recovery systems can recover up to 94% of the input energy used in compression in the form of heat.

Before investing in heat recovery, the end user can calculate the potential energy and cost savings of implementing heat recovery by assessing the heat or hot water demand in areas where practical adjacent to the compressor installation. This assessment can then be compared to the average operating hours of the existing compressed air system, which will highlight the possible payback in terms of the immediate reductions in fuel, oil and gas costs.

With energy consumption typically the biggest target for engineering operators when looking to make savings and improve efficiency, designers and engineers have invested much time and effort in recent years into developing energy efficient compressed air solutions. This is a core mission at BOGE, where the growing popularity of heat recovery has led to the recent extension of the Duotherm heat recovery product range, now available as an external, stand-alone model.

As well as recovering up to 94% of the input energy used in compression in the form of heat the Duotherm heat recovery system is also compact, with only a minimum space requirement, and connects into the oil circuit of the compressor with no external energy needed for operation. BOGE provides comprehensive support for businesses that rely on compressed air, so they are able to make substantial energy savings that directly affect profitability.

ISO 11011

It is only possible to make significant, beneficial improvements when there is accurate information about the current performance of a compressed air application, which is why a new standard has been introduced to set the requirements for conducting a compressed air system assessment.

Historically, the lack of any formal standard allowed suppliers with differing levels of expertise to conduct a compressed air audit, and with such a variance in the quality of each evaluation it was difficult to consider any analysis as a conclusive, comprehensive system assessment. The globally accepted ISO 11011 has now created a framework for the compressed air system energy efficiency assessment and auditing process.

BOGE Compressors Ltd has been accredited to Compressed Air Energy Efficiency Assessment Standard ISO 11011. The achievement recognises BOGE’s commitment to providing comprehensive and detailed energy audits, which extend its customer support services and enable compressed air users to optimise their energy usage and identify actions that can reduce costs. BOGE Compressors Ltd is the daughter company of BOGE KOMPRESSOREN Otto Boge GmbH & Co. KG, based in Germany. BOGE manufactures a comprehensive range of oil lubricated and oil-free screw and piston compressors used by all sectors of industry to supply compressed air for a wide range of manufacturing processes. It also supplies a complementary range of filters, dryers and condensate management equipment. The product is sold and serviced through a dedicated network of 36 distributors throughout the UK and Ireland. See .

Author: Mark Whitmore, general manager, BOGE Compressors Ltd
Cutting energy consumption is almost always the best way to enhance plant efficiency and there are now a number of tools available with which to evaluate, manage and reduce consumption. For example, nearly all of the energy that is used to power an...

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